Preventing the overflow of liquid metal from an end casting head discharged in a curved continuous casting path towards the horizontal plane



Oct. 1o, 1967 KA Rum-:ORG sPElTH ETAL 3,346,035 PREVENTING THE END OVERFLOWOF LIQUID METAL FROM AN CASTING HEAD DISCHARGED IN A CURVED CONTINUOUS CASTING PATH TOWARDS THE HORIZONTAL PLANE Filed Feb. 18, 1965 /nvenora United States Patent O 3,346,035 PREVENTING THE OVERFLOW OF LIQUID METAL FROM AN END CASTING HEAD DISCHARGED IN A CURVED CONTINUOUS CASTING PATH TOWARDS THE HORIZONTAL PLANE Karl-Georg Speith, Duisburg, and Adolf Bungeroth, Duisberg-Huckingen, Germany, assignors to Mannesmann Aktiengesellschaft, Dusseldorf, Germany, a corporation of Germany Filed Feb. 18, 1965, Ser. No. 433,752 Claims priority, application Germany, Feb. 20, 1964, M 59,992 3 Claims. (Cl. 164-82) The invention relates to continuous casting and relates more particularly to the continuous casting in a curve`d discharge path of steel lbillets in which the descending billet is deflected to the horizon-tal plane and wherein during the normal cas-ting operation the liquid sump projects with its leadin-g poin-t and a portion to the rear thereof to a minor and major extentinto the horizontal plane.

During the continuous casting operation in the aforesaid manner, there exists the hazard that when the continuous casting operati-on comes to an end and the last piece of the casting in form of an end casting head descends out of the mold and gradually is transported into the horizontal position, liquid steel may spill or overflow or liow out of the end casting head; on this occasion, indeed, the entire remainder of the still liquidy sump may be spilled through the opening of the end casting head, as soon as the end head of the billet enters into the horizontal. Such a spil-ling would, of course, have a core deteriorating effect.

Even if at the end of the casting operation a much reduced ferrostatic pressure enables the forming of bi1- lets without any deterioration in the core quality, this would presuppose that in the terminal end portion of the billet there is still maintained a mass head effect un-til the llast liquid drop of steel has been solidified in the end head.

The aforesaidV mass head effect operates in a core condensing manner from the beginning until the end of the casting operation, and remains effective for a while even after the teeming of molten steel into the mold has been halted, -namely as long as liquid steel descends alone in the casting direction into the leading point of the sump which is formed by the converging solidification fronts.

I-n continuous curved casting with a horizontally positioned liquid sump end it is necessary that during idling of the machine no core deteriorating overflow occurs in end head of the billet.

It is accordingly among the principal objects of the invention to restrain during idling of the machine any overliow from the end head of the billet.

It is another object of the invention to provide for a curved-discharge technique with a reduced casting speed at least shortly before the termination of steel delivery or teeming into the mold.

It is still a further object of the invention to reduce the casting speed from the -beginning of the end period of the casting operation.

It is yet another Iobject of the invention to provide for reduction of the cas-ting speed to such a degree that the leading point of the liquid sump will recede along the curved-discharge path of the billet to a position above and in advance of the horizontal plane.

v 3,346,035 Patented Oct. l0, 1967 With the above and other objects of the invention in view, t-he invention consists in the novel methods, construction, arrangement and combinations of various devices, elements and parts, as set forth in the claims hereof, one embodiment of the same being illustrated in the accompanying drawing and described in the specification.

In accordance with the invention, lthe aforesaid drawbacks attendant upon overflow can be avoided by reducing the casting speed at least shortly before steel delivery into the mold ceases. Reduction of the casting speed is preferred when the end periodof the casting operation sets in. In any event the reduction of the casting speed should be suicient so that the leading point of the liquid sump recedes along the discharge path to a position upstream of the horizontal plane.

In the appended drawing the single view is a schematic side elevational view, partly in section, of a billet during its curved-discharge path after the mold.

Reference is had to the following: The Continuous Casting of Steel, by L. V. Gallagher and B. S. Old, Scientific American (December 1963), pp. -88.

Referring to the drawing, when the normal liquid sump stretch SN, which equals percent, during the casting operation is positioned with its leading point at x percent of the horizontal, its length before the end of the casting operation should be in good time reduced to the value SE in `accordance with the formula sE sN(1'o0-x) percent This is achieved by reducing the normal casting speed VN=100 percent to VE VN(100-x) percent; wherein the leading point of the sump is caused to recede back Ito the desired position. This recession always needs a period of time which corresponds to the billet solidiiication time T. The pre-calculated reduction in casting speed must therefore be applied at the latest T minutes before the end of the billet solidilication, or at the latest when the steel delivery to the mold stops.

Example In casting a billet of an edge length of 200 x 200 mm. the casting speed VN is assumed to be 900 mm./rnin. Under these conditions-at constant cooling-the length of the liquid sump SN is 8 m.

In a curved-discharge casting machine the distance of the liquid sump of 8 m. is situated for a stretch of about 6 1n. in the curved portion of the billet and the remainder which equals about 2 m. is disposed in the horizontal plane. Before the idling of the machine, the length of the sump should be diminished for more than 2 m.for instance, for 2.5 m.-to about 5.5 m.

This is done by correspondingly reducing Ithe speed VN=9O0 mm./min. to the end speed VE at the moment of discontinuing the casting operation:

At the instant of termination of the cast-ing operation (at the end of steel feeding), the casting speed must be reduced to 620 mm./min. and continuing at a reduced Withdrawal speed sufficiently long so that the leading snmp point will recede in the horizontal towards the casting head in the casting curve and will coincide with the end head before the horizontal is reached.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown 3 and described, for obvious modifications will occur to a person skilled in the art.

Having thus described the invention, what we claim as new and desired to be secured by Letters Patent, is as follows:

1. In a method of preventing the overow of liquid metal from an end casting head of a casting discharged in a cu-rved continuous discharge path towards the horizontal plane during the terminal period of the casting operation, the steps comprising, reducing the casting speed at least shortly'before the end of the steel delivery to the mold to reduce the length of the sump and contin-ning 'withdrawal at a reduced casting speed so that thereafter the leading point of the sump is maintained above the horizontal.

2. In a method, as claimed in claim 1, the reduction ofthe casting speed commencing at the beginning of the terminal period of the casting operation.

3. In -a method, as claimed in claim 2, the reduction of the casting speed being suicient so that the leading point of the liquid sump which during the preceding normal casting operation was positioned at a point in the :horizontal plane, will be forced to recede along the path to a position upstream of said point and above the horizontal plane.

References Cited Continuous and Pressure Casting, published by Association of Iron and Steel Engineers, Pittsburgh, Pa., 1964, p. 14.

J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant!I Examiner. 

1. IN A METHOD OF PREVENTING THE OVERFLOW OF LIQUID METAL FOR AN END CASTING HEAD OF A CASTING DISCHARGED IN A CURVED CONTINUOUS DISCHARGED PATH TOWARDS THE HORIZONTAL PLANE DURING THE TERMINAL PERIOD OF THE CASTING OPERATION, THE STEPS COMPRISING, REDUCING THE CASTING SPEED AT LEAST SHORTLY BEFORE THE END OF THE STEEL DELIVERY TO THE MOLD TO REDUCE THE LENGTH OF THE SUMP AND CONTINUING WITHDRAWAL AT A REDUCED CASTING SPEED SO THAT THEREAFTER THE LEADING POINT OF THE SUMP IS MAINTAINED ABOVE THE HORIZONTAL. 